Atomizer



Oct 7, 1952 Filed A ril 50, 1947 J. FLETCHER ATOMIZER 2 SHEETS-SHEET 1 INVENTOR James Fletcher I BY ATTORNEY Oct. 7 1952 Filed April 50, 1947 J. FLETCHER ATOMIZER 2 SHEETS-SHEET 2 INVENTQR James Fletcher ATTORNEY Patented Oct. 7, 195 2 2,613,112 ATOMIZER James Fletcher, Akron, Ohio, assignor to The Babcock & Wilcox Company, Rockleigh, N. J acorporation of New Jersey Application April 30, 1947, Serial No. 744,891

The invention herein disclosed relates to the construction and operation of fluid dispersal apparatus adapted particularly for the dispersal of liquid fuel in the formof a spray presenting an extensive area of particle surface to an adjacent combustion supporting atmosphere.

.An important feature of my invention is the provision of apparatus arranged for the atomization of liquids of various physical characteristics through the action of a suitable atomizing fluid such as air, steam, or other gaseous medium, such liquids including, especially, liquid fuels of the heavier grades and higher viscosities, such as heavy oil, tar and black liquor.

Another important feature is the provision of a particular form of spray wherein the normal ex,- pansion in cross section is maintained substantially greater in one direction than in a direction normal thereto. V

More specifically, my invention has for an object the spraying of liquid from one or more outlet orifices in the form of a fiat spray of generally oblong cross section throughout.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming .a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its .use,

illustrated and described selected embodiments of my invention.

Of the drawings: r Fig. l is a longitudinal assembly view, in section, of an atomizer constructed in accordance with my invention;

Fig; .2 is an enlarged fragmentary Fig. 1 taken along line 2-2;.

Fig. 3 is an end view of parts shown in Fig. 2; Figs. 4 and 5 are transverse sections of Fig. 2,

taken along lines 4-4 and 5-5, respectively, as

viewed in opposite direction from a common plane; 1 Fig. 6- is a fragmentary longitudinal section of Fig. 2 taken along line 68;

. Fig. 7 shows a modified form of sprayer plate asviewed from the fiuid inlet side;

Figs. '8 and 9 are longitudinal sections of Fig. 7

section of 14 Claims. (01. 299--140) I4 therein and separably connected to a coupling member 15 providing inlet connections 16 and 11 for the separate admission of fiuids to such passages. An outer tube or barrel [8 and an inner tube 19, coaxially arranged and each connected at one end to body member 12, provide an outer annular fiuid supply passage 21 in communication with body passage 13 and a centrally disposed fiuidsupply passage 23 in communication with. body passage 14.

A sprayer head or nozzle 24 is secured at one end to the inner end of tube 19 as by threads 25 and at its opposite end is formed with a flange 26 seated within a counterbore 21 at the inner end of atomizer barrel l8, and providing a planar joint surface 28 against'which a sprayer plate 29 is assembled. The nozzle 24 is formed with a central passage or bore M in direct communication with the central fluid supply passage 23 and in its outer end surface 28 is formed with an annular recess or groove 32 having communication with the annular fluid supply passage 21 through a series of circumferentially spaced holes 34 extending, from the base of the recess through flange 26. Fluid admitted through inlet 15 is thus conducted to the sprayer plate 29 at joint surface 28 through body passage I4, central inner tube passage 23, and nozzle bore 31, while fluid admitted through inlet 11 is conducted through body passage l3, annular barrel passage 2|, cir- "cumferentially spaced holes 34 and annular recess 32.

The sprayer plate 29, as shown, is of one-piece construction having a rearward base surface 35 .of which the major portion isof annular formation in a plane normal to the central longitudinal axis of the atomizer assembly, the plate surface 35 being maintained in fluid tight contact with the nozzle end surface 28 by means of a cap 36 having an inturned flange portion 3'1 engaging a circumferential base flange portion 38 of the piece, serving as a shield for the assembly and as an atomizer supporting member.

The sprayer plate 29 is formed with a single discharge orifice providing a substantially flat spray of oblong cross section in planes normal to the axis of fluid discharge, the orifice or port 45 being in the form of a diametrically arranged .slot having parallel side walls 46 joined at their ends by. arcuate surfaces 41. The forward end surface 48 of plate 29 is formed as a surface of revolution about the central axis of the plate and tubular atomizer assembly, the surface 48 includin a major conical portion 49 having side wall 5 portions inclined to the central axis at an angle of about 45 and thereby defining an included angle of about 90 the surface '48terminatingaint a spherical tipportiontl determining a' total axial dimension of sprayer plate generally less 11) than its maximum diameter at its base. 1 Referring to Figs. 2 and 3 in particular, the outwardly curved end walls 41 include inner end portions 52 arranged normal to bas -surface 35- and thus parallel to each other an'dtc' i'th'e-central'15* axis for a portion of the distance through plate 29, the outer end portions 53 of? suchswallssdi verging from the central axis and from eachother and terminating in substantially right angledrelation to the conical forward surface portion 49 of .i the plate, the end wall surface portions 52 and 53 being joined byl a rounded transitioz-r sure face 54 of suitable radius; 'Ihev entrance :touslot 1 45 -is-'enlarged to the diameter of the: nozzle bore 3[ --by':means of a conicalasurfacefifilwhich ex'-: tendsfr'om the plane 'ofbase surface =35L at: an. angle of about 45? and interscts each:side 1 and end 1 wall of 4 the slot. in a curved line-51r.' Fluid inlet ports 58, having circumferentially spaced in:

let openings 59 in the annular p'ortion" of base' 35, extend at an inclinationltozlthe-tbase to-intersect the-side and: end walls of slot 45zinltwogrou'ps of outlet openings. 61: discharging into the: slot A from opposite directions. The ports:58 :are ars. ranged in groups :at opposite sides Iotith'e centr'al longitudinal plane A-A of slot '45, with the :ports of'each group inclined at an angle of about- 45 to plane AJ-A; and with the longitudlnal axis 0f each' port in a plane normal to= plane A".-'A;.. The-- ports 58 thus have their. longitudinal axes in par- 40' allel' planes although, asswillbe noted: from:-Fig; 5, the longitudinal. axis planesaof fports-58 at one-- side of... slot plane A+A are -displaced '-from--th'e: longitudinal axis planes-of portsi58 at theloppo' site' side, thereby. providing. outlet openings 61. in

vlded, it-isdesirable in maintain the sprayer plate -29 in predetermined angular; relation m such parts of the atomizerassembly-as are normally installed so as to beheld'in'a' fixed angu-. lar position. For'this purpose, one or more dow- I els 6-2 may be employed, extendingirom nozzle 24 into a socket or "sockets B3 in sprayer plate. 29, and thereby providing-a positive indexlngor keyin means whereby the sprayer plate mays-be repeatedly assembled into-the same-angularposition to maintain a-predetermined angular post-- tion for-the spray,- axis A'-A.- Inthearrangement shown, it maybe assumed that' the dowels- 62 and nozzle passages 3.4: ar'e circum-ferentiallyarranged so as to maintain the 'spray'ax-is A-'-'A in a horizontal position, or at least paral-lel to a horizontal line. It"W-ill be understoody how' ever, that the circumferential arrangement of such dowelsand passages may be altered to Provide' otherangu-lar positions of the s ray "axis as might be determined by the particular environment of operation.

Figs. 7-9 show a modified form of sprayer plate II also providing a generally flat fan-shaped pattern of spray, and adapted for incorporation in an atomizer assembly such as is illustrated in Fig. 1. Plate II is of substantially the same proportionsi-asplatelll whereby the total 'axial dimension of plate' H is generally 'lessthan the maximum plate diameter at its base. In this embodiment of the invention, the total fluid discharge area is provided by separate outlet ports 12 having their longitudinal axes in a common diametral plane as; indicated by the section taken alongline 8 8fi'-of-Fig. 7. Ports 12 are arranged ifidiverging'relation' with respect to each other and,inthe arrangement shown, are formed about axes diverging from a common point on the central longitudinal axis of the circular plate, one port of the series being centrally disposed and in alignment with thecentral axis. The ports 12-extend entirely through theplate from arowl of inlet openings 13 in the rearward; plate-:sur-s face 14, to a row 'ofoutlet.openingsfl5in thei forward plate "surface 1.6, each port .12 having-its outlet end portion 18-0f greater diameter: than its inlet-end portion' 19 for reasons: which .are

later made apparent. As shown, the rearward surface! comprisesanouter annular surface portion 8l arranged in a. plane-:normal to, the

central axis; together with av centrally disposed inner-surface portion 82-. in which arenformedi the inletopenings l3, thecentral portion 82 'be-- ing formed as a recess-.havlngan end wall 831 parallel to the-base surface" portion 8l,.and a conical sideiwall portion 84 defining .an includedangle usually less than 90;

The ports 12' extend at right angles; to the" forward plate surface 16 which is approximately; :sphericalin contour, .being formed of successive conical portions 85" and 86. arranged annularly;

of a. centrally disposedv planar portionx8l parallel to the central recesssurface Bzl. Theportsor holes. 12 may. thus: be' readily. drilled from the forwardsurface 16'and,'being.-.of circular cross section, provide discharge openings 15 having:

substantially circular rims. contributing to subs stantia-l uniformity: of jet discharge from. allports.

Avsecond seriesvof' holes :or ports .89, suitablyxof circular cross section and .having..circumferen-v ti'ally. spaced inlet openings 9|. in th -annular:

base surface 8|, extend partially through plate- H to form junctures with ports-12 at :their enlarged outlet ends 18,.closely. adjacent the .base

portions-thereof. Ports 89 aresymmetrically arranged in circumferentially spaced groups, one

group ateach side of the IOWf'Of ports", with the longitudinal axes: of ports. 89 '-in' parallel:

planes normal to therplane' of the row of ports 12, and with the longitudinal axes of ports.89 of each group. parallel to each: other"and.'ar-t ranged at substantially. equal inclinations to the-z plane of ports 12, the angle of inclination being suitablyrof the. order of about 30 to 45::degrees.

In the arrangement shown,,eaclr porti 12lis thus intersected by. two ports; 89:. entering from opposite sides and having. their longitudinal axes:

in acomm'on' plane to intersectin a point on 0 the: centerline of a"port 'lz within its -en1 '1" .6d'

cated in Fig. 1, the dowels" 62 are-omittediand thecorrectangular position of the plate deteris" substituted. for" mined by inspection,-the clamping effect of cap 36 being relied upon to maintain the sprayer plate in the desired assembled relation to the remainder of the assembly; otherwise dowels B2 and dowel sockets 63 may be included as in Fig. l, as will be understood.

The sprayer plates thus described are adapted for spraying liquids of various grades and viscosities as previously indicated, including for ex ample such liquid fuels as oil, tar, sludge and the concentrated liquors resulting from various pulping? processes. When used for spraying liquid fuels, the particular pattern of spray is oftena distinct advantage in heat recovery units where the more conventional conical pattern of spray would not be suitable. In certain installations, while the character of fuel may be one controlling factor, it may also be necessary to adopt the flat fan-shaped pattern to provide the desired relation to anexisting or contemplated sourceof combustion air, or to other fuel firing apparatus using gas, coal, oil, or other fuel.

The form of sprayer plate 29 makes it particularly adaptable for spraying residual liquor, mainly because of the provision of a single fuel port 45 in which the total required fuel flow area is continuous and centrally disposed, and in axial communication with fuel supply passage 23, whereby plugging with this type of fuel is obviated. The residual or black liquor is thus ada mitted through inlet [6 and passes from the central atomizer passage 23 direct to the diametral sprayer plate port 45. The gaseous atomizing fluid, suitably steam, is admitted through inlet l1 and passes from the annular passage 2| to the groups of sprayer plate ports 58 for discharge into port 45 in obliquerelation to the fuel stream flowing therethrough. Such confluence or juncture of the atomizing fluid streams with the stream of fuel results in atomization of the liquid through inlet [1, then the fuel is directed through sprayer plate ports 12 and the fuel atomizing medium through opposing groups of ports 89, the resulting atomized fuel being discharged in a series of'jets through the row of outlet openings 15 to provide a flat fan-shaped form of spray.

While in accordance with the provisions of the statutes l have illustrated and described herein the best form of myinvention nowknown to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of theinvention covered by my claims, and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

I claim:

1. Apparatus for spraying liquid in a fans'haped pattern; comprising a sprayer plate having a. rearward and a forward surfac'e'transversely arranged relative toa common rectilinear axis, means defining a fluid directing path through said plate from on of said surfaces to the other,

said-path being'of symmetrical formation relative'to a median plane containing said axis and providing a total flow area throughout of greater dimension in said median plane thanin a. plane normal thereto, said plate having fluid inlet ports extending partially therethrough from said rearward surface and individually forming junctures with said fluid directing path, said ports being arranged in spaced groups respectively at opposite sides of said median plane and being cylindrically formed throughout about straightline axesparallel to said normal plane, each port of each of saidgroups opening into said fluid directing path intermediate opposite ends of said path and at an acute angle relative to said median plane.

2. Apparatus for spraying liquid in a fanshaped pattern comprising a sprayer plate having its body portion of circular formation about a central axis and having a rearward and a forward surface arranged transversely of said axis, said plate having a liquid conducting path ex,- tending therethrough from said rearward to said forward surface, said path having its inlet in a central portion of said rearward surface to which said liquid is supplied throughout the entire area of said inlet, said path providing a total flow area throughout of greater dimension in a median plane containing said axis than in a direction normal to said plane, said flow area throughout said path being diametrically distributed in symmetrical relation to said axis and terminating at said forward surface at greater distances from said axis than at said rearward surface, said plate having ports extending partially there'- through from an annular portion of said rearward surface and individually forming junctures with different portions of said liquid conducting path at points rearwardly spaced from said forward surface, said ports being arranged in spaced groups respectively at opposite sides of said plane and in the respective groups being formed throughout about parallel straight-line axes in clined toward said median plane in the direction of said forward surface.

3. A sprayer plate having a bodyportion of symmetrical formation about a central axi and arranged to discharge liquid received therein in the form of a flat spray having its major axis of cross section in a plane containing said axis, said plate having a port extending therethrough from a rearward to a forward surface thereof and throughout its axial extent providing a fluid flow area elongated in a direction paralleling said plane, said port providing an entrance area in said rearward surface for receiving an atomizable liquid and providing an outlet area in said forward surface for discharging said liquid in said flat form of spray, said plate being formed with ports arranged in spaced groups respectively at opposite sides of said plane and providing circumferentially spaced inlet areas in said rearward surface for admission of a gaseous atomizing medium thereto, said last named ports extending partially through said plate and individually terminating in junctures with said first named port at points inwardly spaced from both said surfaces, said last named ports being formed throughout about straight-line axes disposed in parallel planes arranged at right angles to said first named plane.

4. A. sprayer plate having a body portion of circular formation about a central axis and arranged to discharge liquid received therein in the form of a flat spray having its major axisof cross section in a diametrical plane, said plate having diam-11c a .upafallehsided zgport :extending 'r-therethrough fromaa rearwardto:a.-forwarclsurface thereofand .-throu hout:its:.axial extent providing ;a fluid flow path of:oblon .;cross section having its major-axis continuously" in ,said; iplane, ;.said port having its inlet insaidrearward-surface, for-receiving said liquid and having its .outlet in said forward surfacelfor discharging. said liquid, in said flat form ofsprayr'saidplate :being formed with ports varrangedclinygroupsdat opposite sides. of saidplane and .havingcinlets :inrsaidrrearward surface for admision ofra;gaseoustatomizing medium thereto, said lastnamedtports extendingrpartially through said plate-and individually:terminating in spaced relation to both said surfaces in junctures .with said liquid receiving.-port,.-;said lastinamediports in .each:of;said, groups'rbeingrformed throughout about :parallelrstraight-iine. axes .inclined toward said diametralplane; in the direction-of i said .forward surfacersaidzlastnamed :ports in. the respective :groups :.having outlets in opposite .sides' of said parallelesidedmortat interspersed positions parallelingisaidrmajoraxis.

Ti'5.J-A sprayer :plate of zone-piece =,construction having. one or 'morezports extending therethrough and constituting a :fluid flowpath adapted to receive liquid fuel;.at :one end :and to discharge .saidrfuel in aSflat-form-of spray:from'itsropposite end, saidxpath .havingjits'zflowiarea substantially evenlydistributed withzrespect to aanedian-plane of ilowzand ;also 'with :respect 170 5a plane normal thereto, said "flow :path from .one .cnd thereof to the: other zprovidinggazfiow area more-widely distributed iinica .directiongparallel .to :said .-median plane than: inn-a adirection pgnormal thereto, .said flow; area increasing ;toward .said discharge end to. azmaximuxm at.said:end,1said-plate havin ports extending in;;continuous lengths from saidtone endof said plate to said fluid flow pathzand'arranged. to direct :a fluid atomizing medium into saidzpathatlocations of increased flow area inwardly-spaced :from :bothsaid surfaces,.:said.;last named ports respectively .zforming continuous straight-line passages of :circular cross-section throughout and enteringrsaid pathz'at acuteangles .from opposite-.sides-of saidmedian plane.

a 6. A :sprayerrplate :having a port extending Ztherethrough and constituting a fluid fiowpath adaptedito receive anuatomizable fueliatone: end and todischargesaid fuel :in an atomized .state :from its :opposite 'end, said port having: parallel side walls at opposite sidesof :a median plane: and having opposing end .walls symmetrically arrangedwith respect to a central axis in said plane, :sald endawalls paralleling said axis adjacent said fuel-receiving end and diverging from .said axis toward said fuel-discharging end, :said-plateihav- .ing sports extending partially .therethrough from .an-exterior surface thereofzandarranged-to direct a :fiuid atomizingzmedium. into said path from'op- .posite sidesnof said-median plane, said last named ports respectively forming continuous straight- :line passages of ::circular cross-section entering said :path at substantially equal inclinations to said medianplane 1 at "locations 'rearwardly displaced from the discharge end of saidipath.

;7.A sprayer .plate of one-piece construction having a :port extending therethrough and I forming a .transversely scontinuous flow, path -of ;oblong cross section having its .majoraxis-in a median plane,:said port .having an inlet for liquid fuel in ayrearward :exterior surface :of said plate (and having an .outlet-for atomized fuel in; a for- :wardexterior surface thereof, said -;port having gparallel side walls equidistantfrom said median pl-anerthroughoutthezlengthof-saidportandhdV- ingiopposing ends-wallssymmetrically arranged withrespect .to a central axis in said-plane; said forward surface .being; .convexedly'rformedhas-la surface of. :revolution about saidaxis, said .-end Walls including portionsadivergingtfromsaid axis toward said rforward surface :and .-.terminating thereat :in substantially normal relation thereto, saidplate-having ports extending partiallyth'erethrough cfrom said:rearwardsurface and-individually iterminatin atisaid. side walls -j unctures withrsaid first named port "at opposite-sides of'said median; plane-said junctures :being ;located=rbetween: said surfaces-at ;substantially :thebase :of said diverging. end wallportions, said :p1ate:b.eing solidlrthroughout;exceptlfor therspaces coccunied byrsaid ports.

8. .A...;sprayer plate thawing .:.a i iirstzrseries :of ports 3EXlJfiI1Cling1fth8l-Bllh1'0llgfl rand ziconstituting fiflflllldifflOWi path ;:-a;dapted sto receive liquidzat one 75116122114121?!) .dischargersaidzliquid in amatomized estate-from itsopposite. end; said portsdravingilongitudinal .axes iarrangedxin :diverging re- .lation' to iea'chiiotherz-in-a:commomplane'totqarovide :a ffaneshaped';spray,.::said plate chavingua 'secondrseries. :of: ports: extending :partially .therethrough-andarrangeditoi discharge ra rluid atomizing mediumrinto'ports. of saidzfirstrserieaxsaid ports of said second. series being arranged sat opposite sidesrofisaidicommomplane and having longitudinal .gaxes ;disposedxrinzzplanes:normalsto said: common plane.

9 A sprayer -platefhavingia first-series;nf;:.pnrts extending utherethrough -;and:'.constituting :aiiluid flow; path adaptediro.:receive. :liquidizat; one rend .and to :dischar ezsaid liquid-iinazan iatomizedxstate from its 'opposite end,.;.saidi ports .;having longitudinalaxes :arranged: 'in .diverging;.relation to each "other in-;a:.common plane'toprovider-a fanshapedspray; said ports being: of 'cylindricaliformation -;throughout :and each "having its outlet ;end -portion .adjacent :a ;'forward 1318138 surface of greater :crosssection than its inlet; end 'portion adjacent a rearward plate :.'surface, :said platexhaving :a :second :series .ofc'ports extending partially .therethrough :from zsaidzrrearwardi'surface :and :arranged to discharge a fluid :atomizing medium into, ports .rOf said first :series, said 'ports of said -secon'cl seriesubeing rarrangeduat opposite sides of said :commonrplane=:and:enter- .ingeach port .:of-,--said :firstv series -in pairs, said ports forming each 30f said rpairs; entering .1 a port of :said firstserieszadjacent the 'hase'onsaidportion of greater crosssection.

10. :Anatomizer :having :an :assembly of concentrically arranged inner and router L-tubular members normally -fi-xed.nagainstrrotationabout acommon. centraIiaXis-and providing -a,;central and-,anannularifluid supply area fora liquidfuel anda fuel-atomizingfiuid respectivelyta sprayer .plate-removably joinedtto said assembly inaxlal relation .theretoand having avfirst and a second .fiuid flow .path arranged-.tosseparately .-receive said'fuel and said fuel-atomizing..fiuidfromsaid areas, said plate bein offgenerally circular formation about said. axis and of smaller dimension longitudinally of said axis thanin a.

direction normal thereto, sai'd'first pathext ing entirely through said plate andproviding a flow area of'diametrically elongated cross section throughout, said first path having .an inlet end portionreceivingsaid liquid fuel throughout its totalelongated cross section .and having aconnecting outlet end portionfrom which said .fuel is discharged-ina .flat spraysubstantially in the plane of said axis, said second path being formed of circumferentially spaced groups of ports restricted to regions at opposite sides of said plane and directing said fuel atomizing fluid into said liquid fuel receiving portion of said first path, said ports forming continuous straight-line passages each having its inlet in an exterior surface of said plate and its outlet in a wall of said first fluid flow path.

11. An atomizer as defined in claim 10 and further comprising keying means disposed between said groups of ports and engaging said sprayer plate and said tubular assembly for positively indexing said sprayer plate in a. predetermined angular position.

12. Apparatus for effecting mixture of fluids delivered thereto and for discharging the resulting mixture in a fan-shaped pattern, said apparatus comprising a fluid discharge plate having a rearward and a forward surface transversely arranged relative to a common rectilinear axis, means defining a fluid directing path extending through said plate from one of said surfaces to the other, said path being of symmetrical formation relative to a median plane containing said axis and providing a total flow area throughout of greater dimension in said median plane than in a plane normal thereto, said flow area increasing toward said forward surface to a maximum at said surface, said plate having fluid inlet ports extending partially therethrough from said rearward surface and individually forming junctures with said fluid directing path at locations of increased flow area inwardly spaced from both said surfaces, said ports being arranged in spaced groups respectively at opposite sides of said median plane and bein cylindrically formed throughout about straightline axes parallel to said normal plane, each port of each of said groups opening into said fluid directing path intermediate opposite ends of said path and at an acute angle relative to said median plane.

13. A sprayer plate having a first series of ports extending therethrough from a rearward surface thereof and having a second series of ports extending partially therethrough from said surface and forming junctures with ports of said first series within the body of said plate, said ports of the respective series having separate inlets in said rearward surface for an atomizable liquid and an atomizing fluid respectively whereby a mixture of said liquid and said fluid is provided at each of said junctures, said ports of said first series having longitudinal axes arranged in forwardly diverging relation to each other substantially in a common plane for discharging the total mixture of liquid and fluid from said junctures in a fan-shaped spray, said ports of said second series being arranged at opposite sides of said common plane and having, longitudinal axes disposed in planes substantially normal to said common plane.

14. A sprayer plate having a first series of ports extending therethrough and constituting a fluid filow path adapted to receive liquid at one end and to discharge said liquid in an atomized state from its opposite end, said ports having longitudinal axes arranged in diverging relation to each other in a common plane to provide a fan-shaped spray, said ports being of cylindrical formation throughout and each having its outlet end portion adjacent a forward plate surface of greater cross section than its inlet end portion adjacent a rearward plate surface, said plate having a second series of ports extending partially therethrough from said rearward surface and arranged to discharge a fluid atomizing medium into ports of said first series, said ports of said second series being arranged at opposite sides of said common plane and each entering a port of said first series adjacent the.

base of said portion of greater cross section.

JAMES FLETCHER.

REFERENCES CITED The following references are of record in the file of this patent:

2,425,710 Bucknam et al. Aug. 19, 1947 

